In many sports which involve the use of a ball, it is often important to not only be able to recognize the direction the ball is rotating, but to recognize this difference quickly. For example, in baseball, one important difference between a fastball, a curveball, a slider, and a screwball is the direction in which the ball spins. Other important factors are the speed of the pitch and rate of spin. Generally speaking, a ball thrown with a spin will curve in the same direction that the front of the ball (home plate side, when pitched) turns. If the ball is spinning from top to bottom (topspin), it will tend to nosedive into the dirt. If it's spinning from left to right, the pitch will break toward third base. The faster the rate of spin, the more the ball's path curves.
In the game of baseball, the pitcher throws a 2.9-inch-diameter ball in the direction of home plate, which is 60.5 feet away from the center of the pitcher's mound; the opponent (referred to as the batter) stands near home plate and attempts to hit the ball with a sturdy wooden bat. The pitcher makes the batter's task difficult by throwing the ball at different velocities and with different spins. One well-known type of pitch, the curveball, travels at about 75 mph with a 1500 rpm spin. The curveball is a physically measurable phenomenon: the imbalance of forces created by the ball's spin causes the ball to deviate from a straight line and to follow a smooth parabolic path. Since you only have about 0.4 seconds from when the ball leaves the pitchers hand to when it hits the catcher's mitt, it is critical to quickly recognize the rotation of the ball.
Typical major league fastballs travel at 90 mph, with a 1200 rpm backspin. Fastballs descend on their way from the pitcher's mound to home plate, but batters often report the perception that fastballs rise. There are two different types of fastballs, a two-seam and a four-seam. The two-seam fastball spins so that the two seams cross the batter's field of view on each rotation of the ball, and the four-seam fastball spins so that the four seams cross the batter's field of view on each rotation).
Similarly in soccer, for example, a goalie will need to quickly recognize the rotation of the ball in order to better position himself to block the ball from entering the goal.
Thus, there is a need for an apparatus which can replicate the spin of an object, such as a ball, under various conditions, and methods of using the apparatus to evaluate a subjects ability to detect the rotation of the object, as well as methods for training subjects to more quickly detect an object's rotation.